XmoppelX114,287 Locked 17 Nov 2011 19 Nov 2011
I first thought they meant the bomb challenges, so i did them first and i don't know if you have to complete them for the achievement.
As soon as you unlocked Piri Reis (at the great basar) you can enter his room, you can find it on the map, he got an extra icon. In his room you can craft bombs, buy stuff from him and so on. On his left-hand side there are 4 paintings you can interact with (by pressing B) each painting gives you 2 short bomb tutorial missions. When I completed the 8 missions the achievement popped.
You only need these 8 tutorial missions for the achievement, the bomb challenges and the "Piri Reis:..." assassin-missions are optional (thanks to Anti Wan Kenobi for confirming!)